VU CS601 – DATA COMMUNICATION FINALTERM Solved Unsolved Past Papers 2005
CS601 Data Communication
Final Term Examination – February 2005
Time Allowed: 150 Minutes
Please read the following instructions carefully before attempting any question:
1. This examination is closed book, closed notes, closed neighbors.
2. Answer all questions.
a. There is no choice.
b. You will have to answer correctly all questions in this examination to get the
maximum possible marks.
3. Do not ask any questions about the contents of this examination from anyone.
a. If you think that there is something wrong with any of the questions, attempt it to
the best of your understanding.
b. If you believe that some essential piece of information is missing, make an
appropriate assumption and use it to solve the problem.
4. Examination also consists of multiple-choice questions. Choose only one choice as
a. If you believe that two (or more) of the choices are the correct ones for a
particular question, choose the best one.
b. On the other hand, if you believe that all of the choices provided for a particular
question are the wrong ones, select the one that appears to you as being the
**WARNING: Please note that Virtual University takes serious note of unfair
means. Anyone found involved in cheating will get an `F` grade in this course.
Total Marks: 60 Total
Question No. 1 Marks : 2
Which of the following best describes a single-bit error?
1 A single bit is inverted
2 A single bit is inverted per transmission
3 A single bit is inverted per data unit
4 Any of the above
Question No. 2 Marks : 2
In fiber optic cable, the signal source is__________ waves
4 Very Low Frequency
Question No. 3 Marks : 2
In an environment with many high-voltage devices, the best transmission medium would be _________.
2 Coaxial Cable
3 Twisted Pair
4 Fiber Optic Cable
Question No. 4 Marks : 2
Which of the following is not a guided medium?
1 Twisted Pair
2 Fiber Optic Cable
3 Coaxial Cable
Question No. 5 Marks : 2
Which multiplexing technique involves signals composed of light beams?
4 None of the above
Question No. 6 Marks : 10
Briefly answer the following questions.
1) After transmitting several frames, the transmitter receives a NAK ‘i’ frame. Describe how the transmitter reacts in the following error control protocols.
a. Go-Back N
b. Selective Reject
2) A communication protocol is an agreement required between two or more communication entities and consists of three essential components. Name and describe briefly each
Question No. 7 Marks : 2
Layer 2 lies between the physical layer and the _______ layer.
Question No. 8 Marks : 10
Solve the following. Show all the work to get full credit.
1) A binary signal is sent over a 3 kHz. Channel. Signal’s S/N ratio is 3162 (36dB).
Calculate the maximum achievable data rate?
2) Find the maximum data rate of a noiseless 4-kHz channel-using Analog encoding
e.g. QPSK with 2 bits per sample?
Question No. 9 Marks : 2
The _______ layer changes bits into electromagnetic signals.
Question No. 10 Marks : 12
The following questions deal with CRC error detecting code.
a. Given a message M = 1010001101, determine the CRC using the polynomial
P = x5 + x4 + x2 + 1.
b. What is the transmitted message T.
c. How does the receiver check whether the message T was transmitted without any
Question No. 11 Marks : 2
Flow Control is needed to prevent ____________
1 Overflow of sender buffer
2 Overflow of the receiver buffer
3 Bit Errors
4 Collision between sender and receiver
Question No. 12 Marks : 12
Draw the digital signals for the bit string 0101 0100 1100 111 using NRZ-I and RZ
encoding schemes. A 0 is represented by a high value and a 1 is represented by a low value.